The long-term goal of this research program is to understand the mechanisms by which visual information is transferred across the vertebrate retina. Although the calcium-regulated release of neurotransmitter is a fundamental feature of synaptic communication, the presynaptic mechanisms that govern neurotransmitter release are not yet fully-understood. This is particularly true at the ribbon-style synapses of retinal photoreceptors and bipolar cells, which play pivotal roles in the throughput of visual information. In this research program, we examine mechanisms by which synaptic vesicle dynamics of bipolar cells and photoreceptors of the vertebrate retina are regulated. A combination of biophysical, molecular, and computational approaches are used. Specific goals are to characterize the roles of synaptic vesicle protein 2 (SV2), an integral synaptic vesicle protein, on neurotransmitter release from the mouse rod bipolar cell. A particular emphasis is to define the role of this protein in setting the gain of the rod bipolar cell synapse. The interplay between Ca2+ and other second messengers on the Ca2+-sensitivity of release and vesicle recruitment will also be examined. In addition, the roles of Ca2+ in vesicle recruitment, mobilization and release will be defined for photoreceptors. Detailed computational models of synaptic vesicle mobilization, recruitment and fusion will then be constructed for bipolar cells and photoreceptors. These models will allow us to perform in silico experiments that predict the pattern and extent of neurotransmitter release from various starting conditions. In addition, they will become instrumental in predicting at which step in the complex neuronal secretory pathway a particular manipulation has its effect. Together, the data obtained from this research program will not only reveal new insights into the regulation of the fundamental process of neurotransmitter release at retinal ribbon synapses, but will reveal novel ways by which the release of neurotransmitter is modulated so as to meet the needs of synaptic signaling under different levels of illumination. Furthermore, these results will position us to better determine and understand the role of specific synaptic proteins implicated in disorders of vision. PUBLIC HEALTH RELEVANCE: Results of this research program will enhance our understanding of how we see, providing information for the development of new treatments that will restore vision or prevent its further loss. In addition, it will provide general information about how neurons communicate that is critical for understanding brain diseases such as epilepsy, dementia and schizophrenia.